This invention relates generally to surgical devices and, more particularly, to a device for attaching an object, such as a suture, to a bone, and to a method of using such a device.
Numerous devices are available to attach objects to bone. Several such devices are discussed in the background section of U.S. Pat. No. 4,898,156 to Gatturna et al. The Gatturna et al. patent describes a suture anchor which comprises a coupling member and an integrally formed barb. The coupling member comprises a generally cylindrical body which has a blind hole opening on one of its ends. A side slot communicates with the blind hole and terminates in an inclined surface intermediate the length of the coupling member. The barb comprises a curved length of material integrally formed on the opposite end of the coupling member which, in its unrestrained state, comprises an arc of approximately 90.degree. of a loop approximately 0.250" in diameter. The barb is capable of being elastically deformed to a substantially straight configuration when desired. In its straightened configuration, the barb is preferably greater in length than the coupling member, as measured along the longitudinal axis.
The suture anchor of Gatturna et al. is intended to be utilized in conjunction with an installation tool which is shown in FIGS. 3-6 of the drawings. The installation tool comprises a hollow sheath and a plunger. To install a suture anchor, the anchor is forced into the interior bore of the sheath such that the barb is elastically deformed into its straight configuration. Initially, the suture anchor is left partially protruding from the sheath so that the blind hole in the end of the coupling member remains outside. A suture is attached to the coupling member by tying a knot in the end of the suture and slipping the knotted end of the suture into the blind hole and threading the body of the suture into the coupling member's side slot. Once the suture is so positioned, the suture and suture anchor assembly is pushed further into the installation tool so that the end of the coupling member is positioned substantially flush with the installation tool's front surface. Either before or after the suture anchor has been loaded into the installation tool and the suture attached to the anchor, an appropriately sized hole is formed in the bone to receive the suture and suture anchor assembly. The leading end of the installation tool is then inserted into the hole and the plunger is driven forward to eject the suture anchor out of the installation tool and into the hole. As the coupling member leaves the insertion tool and the barb approaches the mouth of the tool bore, the length of the barb is progressively released from the confines of the tool's bore, thereby allowing the barb to spring back to its normally curved position. This restoration of the barb's curved state causes the suture anchor to pivot on itself so that the anchor swings itself off-center and engages the bone at three different contact points.
Gatturna et al. state that the suture anchor and the receiving hole in the bone must be properly dimensioned relative to one another if the suture anchor is to properly and securely lodge itself in the hole. A specific relationship between the unconstrained suture anchor diameter, the constrained suture anchor diameter and the diameter of the hole is specified. This relationship requires that the barb be formed of a material which is simultaneously capable of substantial resilience and substantial strength. Modifications of the suture anchor which employ two, three or more barbs are also described.
The suture anchor described by Gatturna et al. is a relatively complex structure which, as noted, must be carefully formed and dimensioned in order to insure proper functioning. It is an object of the present invention to provide an alternative device for anchoring sutures to a bone, which device is relatively simple in design and structure and which is highly effective for its intended purpose.
Another object of the present invention is to provide a suture anchor which may be used to effectively retain sutures within a hole formed in a bone while avoiding the requirement of maintaining exact dimensional relationships between the device and the hole.
Yet another object of the present invention is to provide a novel method of securing a suture to a bone which utilizes the novel suture anchor now disclosed.
These and other objects are attained in a device for attaching an object, such as a suture, to a bone which comprises a relatively rigid elongate body having first and second ends and a central portion between said ends, and means for attaching a suture to the central portion of the body. The elongate body has a longitudinal axis which extends through the first and second ends. The suture is attached to the central portion of the body at a point which is offset from the longitudinal axis so that, when the device is placed in a hole in the bone and a force having a component acting in a direction which is parallel to the longitudinal axis of the device is applied to the suture, the device will rotate causing the ends of the elongate body to engage the bone and prevent removal of the device and suture from the hole. In a preferred embodiment, at least one of the ends of the elongate body is formed as a sharp point. The point is offset from the longitudinal axis and faces away from the axis and the central portion of the elongate body.
One embodiment of the invention is formed from a continuous length of rod-like material. The rod-like material has a generally circular cross-section and is formed in a loop which comprises the means for attaching the suture to the central portion of the body. In this embodiment, the sharp points are defined in part by cross-sectional surfaces of the ends which intersect the longitudinal axis to form acute angles. In a preferred embodiment, the angle formed by the intersection of each cross-sectional surface and the longitudinal axis is approximately 45.degree..
Another embodiment of the invention is machined, stamped or otherwise formed from stock material or powder metal. In this embodiment, an opening is formed in the central portion of the body through which the suture may be threaded. The embodiments described in detail below include "barb" structures formed on the ends for penetrating the bone and preventing removal of the device and suture from the hole.
The invention further comprises a method of securing a suture to a bone using a device of the type described above, which comprises the steps of: forming a hole which extends through a cortical layer of the bone and into a cancellous portion of the bone to a depth which at least equals the length of the elongate body of the device; inserting the device and attached suture into the hole such that the outwardly facing end of the device is disposed inwardly of an inner cortical wall of the bone; and pulling the suture to cause the device to rotate such that the ends of the device penetrate the relatively soft cancellous portion of the bone and come to rest substantially adjacent the inner wall of the relatively hard cortical bone so as to secure the suture in place.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.